Role of IL-35 in sublingual allergen immunotherapy

Abstract

Grass pollen-specific immunotherapy involves immunomodulation of allergen-specific TH2 responses and induction of IL-10+ and/or TGF-β+CD4+CD25+ regulatory Tcells (induced Treg cells). IL-35+CD4+CD25+ forkhead box protein 3-negative T (IL-35-inducible regulatory T [iTR35]) cells have been reported as a novel subset of induced Treg cells with modulatory characteristics. We sought to investigate mechanisms underlying the induction and maintenance of immunologic tolerance induced by IL-35 and iTR35cells. The biological effects of IL-35 were assessed on group 2 innate lymphoid cells (ILC2s); dendritic cells primed with thymic stromal lymphopoietin, IL-25, and IL-33; and B and TH2 cells by using flow cytometry and quantitative RT-PCR. Grass pollen-driven TH2 cell proliferation and cytokine production were measured by using tritiated thymidine and Luminex MagPix, respectively. iTR35cells were quantified in patients with grass pollen allergy (seasonal allergic rhinitis [SAR] group, n=16), sublingual immunotherapy (SLIT)-treated patients (SLIT group, n=16), and nonatopic control subjects (NACs; NAC group, n=16). The SAR group had increased proportions of ILC2s (P=.002) and IL-5+ cells (P=.042), IL-13+ cells (P=.042), and IL-5+IL-13+ ILC2s (P=.003) compared with NACs. IL-35 inhibited IL-5 and IL-13 production by ILC2s in the presence of IL-25 or IL-33 (P=.031) and allergen-driven TH2 cytokines by effector T cells. IL-35 inhibited CD40 ligand-, IL-4-, and IL-21-mediated IgE production by B cells (P= .015), allergen-driven T-cell proliferation (P= .001), and TH2 cytokine production mediated by primed dendritic cells. iTR35cells suppressed TH2 cell proliferation and cytokine production. In addition, allergen-driven IL-35 levels and iTR35cell counts were increased in patients receiving SLIT (all, P<.001) and NACs (all, P<.001) compared with patients with SAR. IL-35 and iTR35cells are potential novel immune regulators induced by SLIT. The clinical relevance of SLIT can be underscored by restoration of protective iTR35cells.